Relational schemas are always implicitly stored in the database itself and can be retrieved by querying the database metadata. In addition, relational schemas can be represented by the DDL (Data Definition Language) statements that were used to create the schemas in the first place. However, neither of these formats can be used as a declarative, implementation-neutral format that can be easily stored in a file and used by applications to discover the relational schema.
What is needed is an improved architecture that represents relational schema in a declarative implementation-neutral and/or implementation-specific format.